1. Field of the Invention
This invention relates generally to the field of pressurized plastic containers, and more specifically to a pressurized plastic container that is designed to compensate against any tilting or lateral deflection that might otherwise occur under pressurization as a result of the asymmetry of features such as finger grips that are molded into the sidewall of the container.
2. Description of the Related Technology
A pressurized plastic container is defined as a container that is designed to withstand significant internal pressurization during use. Plastic carbonated beverage containers and plastic aerosol containers both fall within this definition. Carbonated beverages or malt beverages can generate significant internal pressure, on the order of 45-60 psi for malt beverages such as beer. Aerosol containers commonly require internal pressures of the magnitude of 50-300 psi.
Conventional pressurized plastic containers have been designed to have sidewall features that are substantially symmetrical about a longitudinal axis. When a plastic container is pressurized, significant radial and longitudinal forces are applied to the container sidewall. The radial force component has a tendency to cause the sidewall to bow outwardly. Circumferential reinforcement or “hoop strength” must be designed into the container in order to compensate against this.
The longitudinal force component caused by pressurization tends to create a “bellows effect” with respect to features that are molded into the sidewall, which results in elongation of the container. If the sidewall features are not symmetrical about the longitudinal axis of the container, the longitudinal elongation is uneven, resulting in undesirable “tilting” or lateral deflection of the container when it is in the pressurized state. The tilting can be of a magnitude that is noticeable by even a casual observer. In addition, it can cause problems with the automated conveyance and filling of the container at the bottling plant.
Both circumferential and longitudinal deflection can be reduced by increasing the sidewall thickness of the container. However, this increases the material costs to the product manufacturer and ultimately the consumer. The packaging industry is extremely price competitive, and a container design that permits lightweighting of a container without a sacrifice in container performance may have considerable commercial value.
The consumer beverage market is also extremely competitive, and manufacturers of carbonated beverages such as soft drinks and beer look favorably upon packaging that aesthetically distinguishes their products in a manner that complements their product marketing and advertising. In addition, features such as finger grip recesses provide utilitarian advantages to consumers that are in demand. Unfortunately, the introduction of stylized container designs into the carbonated beverage market has been frustrated by the deflection issues caused by pressurization and the lightweighting concerns described above.
A need exists for an asymmetric pressurized plastic container that resists or provides compensation against tilting under pressurization conditions without significantly increasing the material costs of the container.